impious

Diabolic is a synonym of impious.

As adjectives the difference between diabolic and impious

is that diabolic is diabolical while impious is not pious.

As a noun atheist

is atheist.

As an adjective impious is

not pious.

Atrocious is a related term of impious.

As adjectives the difference between atrocious and impious

is that atrocious is frightful, evil, cruel or monstrous while impious is not pious.

Impious is a related term of heathen.

As adjectives the difference between impious and heathen

is that impious is not pious while heathen is pertaining or adhering to the germanic neo-pagan faith heathenry.

As a noun heathen is

an adherent of the germanic neo-pagan faith of heathenry.

As adjectives the difference between impious and pagan

is that impious is not pious while pagan is relating to, characteristic of or adhering to non-Abrahamist religions, especially earlier polytheism.

As a noun pagan is

a person not adhering to any major or recognized religion, especially a heathen or non-Abrahamist, follower of a pantheistic or nature-worshipping religion, neopagan.

As a proper noun Pagan is

a given name derived from Latin.

Impious is a related term of nefarious.

As adjectives the difference between impious and nefarious

is that impious is not pious while nefarious is sinful, villainous, criminal, or wicked, especially when noteworthy or notorious for such characteristics.

Irreligious is a related term of impious.

As adjectives the difference between irreligious and impious

is that irreligious is contrary to religious beliefs and practices while impious is not pious.

As an adjective impious is

not pious.

Diabolical is a synonym of impious.

As adjectives the difference between diabolical and impious

is that diabolical is extremely wicked or cruel while impious is not pious.